Distance Traveled by Hummingbird: Solving for Height

[duckywucky]

Homework Statement

A hummingbird has a mass of about 1.7 g. Suppose a hummingbird does 0.15 J of work against gravity, so that it ascends straight up with a net acceleration of 1.2 m/s2. How far up does it move?

Homework Equations

The Attempt at a Solution

I don't know what to do with the net acceleration, but i do know you have to convert 1.7 g to kg...
what would the formula do you use?!

 

[kuruman]

What does the work-energy theorem say?

 

[duckywucky]

Wnet = delta(KE)

 

[kuruman]

Correct. Can you find numbers/expressions for the two sides of the equation?

 

[duckywucky]

(.0017kg)(1.2m/s^2)

or

(1/2)(.0017kg)(1.2m/s)^2

I'm not sure what to do with the Joules

 

[kuruman]

Wnet = delta(KE)

What does W_net mean to you and how do you think you calculate it?

How about Δ(KE)? What is that all about?

 

[duckywucky]

The Wnet means to me the total work done. and is it Fnet(d)?
KE = 1/2 mv^2 for Δ(KE)?

 

[kuruman]

Correct again. How many different works must be added up to give the total work?

 

[duckywucky]

is it 1.7(1.2) / .15?!

 

[kuruman]

You didn't answer my question. How many different works must be added up to give the total work? In other words, how many forces are doing work here?

 

[duckywucky]

Only 1 force?! the .15 J

 

[kuruman]

Force is expressed in Newtons. The 0.15 J is not a force, it is the work done by the bird as stated in the problem. Now think about this: if the bird did not flap its wings and did not exert that force, would it be suspended in mid-air or would something else happen to it?